Conventional mechanical occlusion devices or coils are used for embolization procedures of AVF, aneurysms, or other vascular lesions. These coils can be deployed accurately to a location, e.g. exactly where the catheter ends. In the human brain, different factors such as anatomic anomalies can occur in the arterial blood vessels, thus forming stretched out sacs or aneurysms. Embolization procedures insert coils that may immediately clot the aneurysm sac, thereby stopping the thinner, weaker sidewalls of the arteries from bulging outward from the main lumen.
Conventional primary coils are either simple coil strands or more complex three dimensional scaffolding of varying shapes. Conventional primary or “framing” coils may be formed in complex three dimensional ball-like shapes. Conventional secondary or “filler” coils may be formed in merely simple arc shapes. Coils are made of metal platinum or stainless steel such that coils are easily seen in radiographic images; however, large coils have a disadvantage in that these can disrupt the radiographic image.
Deploying such conventional coils in an embolization procedure involves deploying the framing coil, for example, the diameter in millimeters of the aneurysm sac is typically measured using the imaging system. A particular diameter of the framing coil is selected that is at or less than the dimension of the diameter of the aneurysm sac such that when the primary coil is extruded from the distal tip of the catheter, at body temperature, the framing coil assumes a three dimensional ball shape within the aneurysm sac. Subsequent additional secondary filling coils are inserted in, around and adjacent the scaffold or framing structure established by the primary coil so as to fully fill the aneurysm sac, thereby promoting the clot.
When using conventional embolic coils, multiple coils (e.g., between 10-12) may be needed to fill an aneurysm. For example, “framework” coils and may be used first to line the outer perimeter of the aneurysm, with softer smaller “filler” coils being used to fill the central portion of the cavity. Examples of three dimensional framework coils that function to clot the vessel of the aneurysms for the therapeutic benefit of the patient are disclosed in the following patents: U.S. Pat. No. 8,323,306 B2 to Schaefer et al; U.S. Pat. No. 6,929,654 B2 to Teoh et al.; U.S. Pat. Publication No. 2003/0120302 A1 to Jaeger; and U.S. Patent Publication No. 2013/0018409 A1 to Burke et al.
Conventional framework coils may have problems adapting to the shape and/or diameter of the aneurysm sac because the unfolded predetermined three dimensional shape does not conform to the specific shape of the aneurysm sac, which is different each time as the aneurysm sac forms in all different shapes. Conventional framework coils may form the intended three dimensional shape in an unpredictable fashion and in a less than optimal fit of the aneurysm sac, thereby necessitating multiple coils for an embolization procedure that increase the cost of the embolic procedure.
Conventional three dimensional shapes also are selected at or below the measured diameter of the aneurysm sac, which may result in three dimensional shaped coils not adapting well to the in-between sizes of a measured aneurysm sac. For example, the aneurysm sack is measured at 4.5 mm and the three dimensional shaped coil is only available at a 4 mm dimension. As a result, conventional treatments first secure a 4 mm three dimensional shaped coil in a measured 4.5 mm aneurysm sac by delivering the 4 mm framing coil to line the outer perimeter of the aneurysm, with softer smaller “filler” coils being used to fill the central portion of the cavity. This further results in numerous coils being used (e.g. between 10-12 coils may be needed) to fill an aneurysm sac. In this instance, there is an increased risk of complications to the patient should a coil or part of a coil such as an end, become dislodged or fall out of the sac into the venial cavity.
Conventional coils may also lose shape if they are kinked, such as by the operation of the catheter. Known catheter systems have no way to retract the coil. If an end or kinked end of the coil, or the entire coil dislodges, from the deployed location there is a significant medical risk that the aneurysm may burst or trigger a clot which then causes distal emboli. Such a bleed can be life threatening or such emboli may result in neurologic deficit.
As such, there is a long-felt need in the art to provide an embolic coil with specific properties of conforming to the specific shape of the aneurysm sac, which is different in each embolization procedure, and to uncoil into a predictable, efficient shape, thereby reducing the risk of prolapse of the coil into the parent vessel. There is a need to reduce number of coils required for the embolization procedure so as to overcome disadvantages of the prior art including increases in the procedure time, cost and risk to the patient. A self-adapting floating diameter embolic coil that conforms to the specific shape of the aneurysm sac can have advantages of forming an effective and efficient scaffold structure. An NiTiNOL efficient scaffold structure would result in effective secondary coil filling using other self-adapting floating diameter embolic coils that can reduce drastically embolization procedure time and cost including the number of embolic coils ultimately used.
Another disadvantage of conventional delivery systems embolic coils and methods used in the embolization procedure is that once a coil is positioned, it is necessary to disconnect the embolic coil from the pusher wire. A drawback in the art is that conventional mechanical, electrical and chemical disconnect systems are irreversible disconnects. Improvement in this area would be an advancement in the prior art.
In a conventional mechanical disconnect system, a capture mechanism located on the proximal end of the embolic coil such as, for example, a latch (or trapped ball) captures the embolic coil for pushing/pulling with a secondary wire or cable that extends down the length of the lumen of the catheter, whereby pulling on the cable opens and release the embolic coil from the latch. Mechanical disconnect systems may perform relatively rapidly; however, this required mechanical movement to disconnect has disadvantages as any mechanical movement to free the embolic coil can cause undesirable movement of the placement of the embolic coil such as, for example, leaving a tail of the embolic coil hanging in the lumen of the artery where it can cause turbulence, and other adverse events. Another disadvantage of conventional mechanical disconnect connections is that once released from the latch, the embolic coil is free and no more control can be exerted over the coil.
In a conventional electrical disconnect connection system, a fusible link is used to disconnect the capture mechanism from the proximal end of the coil. In such systems, an electric current is applied to the pusher wire, whereby the current heats and melts a short portion of the pusher wire proximal to the coil. Electrical disconnects generally use a battery and some sort of push button to connect a circuit that includes the battery, the pusher-wire, a fusible link, and in some embodiments a return wire. Other times the return path of the electrical current flows through the patient's body to a body surface reference electrode. Similarly, electrical disconnect connections have disadvantages of coil control, whereby no more control can be exerted on the embolic coil once released and free of the pusher-wire of the catheter. Similarly, in conventional chemical disconnect connection systems a fusible link is used that is chemically releasable so as to disconnect the capture mechanism from the proximal end of the coil.
As discussed, known catheter systems have no way to retract and/or recapture the coil. If an end of the coil, or the entire coil, dislodges from the deployed location, there is a significant medical risk that the aneurysm may rip or burst, which can be life threatening. As such, there is a long-felt need in the art to provide an embolic coil and delivery system and method of treatment that can recapture and, therefore, control an embolic coil. There also is a related need to reduce embolization procedure time, cost including the number of embolic coils used, and health risks.